Light PollutionDescribe some of the major causes of light pollution and demonstrate an understanding of why it is undesirable to astronomers
Optical pollution is light from human sources. If you go to the countryside or area outside a town on a clear night you will see many more stars than you would do in the city. The reason why you cannot see so many stars in a city is light pollution.
This is the result of so many lights in a built up area shining upwards and obscuring the night sky. There is a Campaign for Dark Skies which advises local authorities on planning city lights.
Chemical pollution comes from man-made and natural chemicals in the atmosphere obscuring the sky or affecting observations.
Human pollution comes from many sources such as manufacturing and production industries. Natural pollution comes from volcanoes and gases from the mantle passing through the crust into the atmosphere. Volcanic ash in particular not only covers the sky and travels around the globe but refracts light substantially.